Managing temperature in an exhaust treatment system

ABSTRACT

A method of controlling an exhaust treatment system includes sensing a temperature representative of a catalyst material temperature at start-up of a power source and comparing the sensed temperature to a threshold temperature. The method also includes igniting a regeneration device of the exhaust treatment system in response to the comparing. The regeneration device is disposed upstream of the catalyst material. The method further includes operating the regeneration device at a target temperature.

TECHNICAL FIELD

The present disclosure relates generally to an exhaust treatment systemand, more particularly, to managing the temperature of one or morecomponents of an exhaust treatment system with a regeneration device.

BACKGROUND

Internal combustion engines, including diesel engines, gasoline engines,natural gas engines, and other engines known in the art, may exhaust acomplex mixture of air pollutants. The pollutants may be composed ofgaseous compounds, which may include nitrous oxides (NOx), and solidparticulate matter. Particulate matter may include soluble organicfraction, soot (unburned carbon), and/or unburned hydrocarbons.

Due to increased attention on the environment, exhaust emissionstandards have become more stringent, and the amount of pollutantsemitted to the atmosphere from an engine may be regulated depending onthe type of engine, size of engine, and/or class of engine. One methodthat has been implemented by engine manufacturers to comply with theregulation of these engine emissions is exhaust gas recirculation (EGR).EGR systems recirculate the exhaust gas byproducts into the intake airsupply of the internal combustion engine. The exhaust gas directed tothe engine cylinder reduces the concentration of oxygen within thecylinder and increases the specific heat of the air/fuel mixture,thereby lowering the maximum combustion temperature within the cylinder.The lowered maximum combustion temperature and reduced oxygenconcentration can slow the chemical reaction of the combustion processand decrease the formation of NOx.

In many EGR applications, the exhaust gas is passed through aparticulate filter configured to capture and/or otherwise extract aportion of the soot, soluble organic fraction, and/or unburnedhydrocarbons contained carried by the exhaust. After a period of use,the particulate filter may become saturated and may require cleaningthrough a regeneration process wherein the particulate matter is purgedfrom the filter. In addition, the particulate filter may include one ormore catalyst materials configured to oxidize a portion of the soot,soluble organic fraction, and/or unburned hydrocarbons contained withinthe exhaust gas. The catalyst materials may also assist in reducing NOxand/or carbon monoxide present in the exhaust.

The catalyst materials may be most effective at temperatures in excessof their passive regeneration or “light-off” temperature (thetemperature at which the catalyst materials are capable of spontaneouslyoxidizing particulate matter). Thus, the catalyst materials are said tohave a relatively high conversion efficiency above their light-offtemperatures, and peak conversion efficiency of the materials may occurin the range of approximately 300 degrees Celsius to approximately 450degrees Celsius. At relatively low temperatures, however, such as, forexample, during engine start-up or during a prolonged idling period, thecatalyst materials may not be capable of oxidizing the particulatematter. As a result, the amount of pollutants emitted by the system mayexceed the maximum emissions limits set forth by the EnvironmentalProtection Agency when the catalyst materials are at relatively lowtemperatures. Such operating conditions may be characterized by anincrease in the amount of whitesmoke exiting the system as well as anincrease in the intensity and amount of unpleasant odors given off.

As shown in U.S. Pat. No. 6,427,436 (“the '436 patent”), a filter systemcan be used to remove particulate matter from a flow of engine exhaustgas before a portion of the gas is fed back to an intake air stream ofthe engine. Specifically, the '436 patent discloses an engine exhaustfilter containing a catalyst and a filter element. A portion of thefiltered exhaust is extracted downstream of the filter and is directedto an intake of the engine through a recirculation loop.

Although the filter system of the '436 patent may protect the enginefrom harmful particulate matter, the system may not be configured toimprove the effectiveness of catalyst materials located in the system byactively increasing the temperature of the catalyst materials to apredetermined temperature within their peak conversion efficiency range.

The disclosed exhaust treatment system is directed to overcoming one ormore of the problems set forth above.

SUMMARY OF THE INVENTION

In one embodiment of the present disclosure, a method of controlling anexhaust treatment system includes sensing a temperature representativeof a catalyst material temperature at start-up of a power source andcomparing the sensed temperature to a threshold temperature. The methodalso includes igniting a regeneration device of the exhaust treatmentsystem in response to the comparing. The regeneration device is disposedupstream of the catalyst material. The method further includes operatingthe regeneration device at a target temperature.

In another embodiment of the present disclosure, a method of reducingthe emissions of an internal combustion engine includes igniting aregeneration device fluidly connected to the internal combustion engineand increasing the temperature of a catalyst material to a targettemperature during a low exhaust temperature operation of the internalcombustion engine. The method also includes maintaining the temperatureof the catalyst material at the target temperature for a predeterminedperiod of time.

In yet another embodiment of the present disclosure, an exhausttreatment system of a power source includes a catalyst material and aregeneration device disposed upstream of the catalyst material. Theregeneration device is configured to increase a temperature of thecatalyst material to a target temperature at start-up of the powersource and in response to a sensed parameter of the exhaust treatmentsystem. The system further includes a particulate filter configured toextract components from an exhaust flow of the power source.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic illustration of an engine having an exhausttreatment system according to an exemplary embodiment of the presentdisclosure.

FIG. 2 is a diagrammatic illustration of an engine having an exhausttreatment system according to another exemplary embodiment of thepresent disclosure.

FIG. 3 is a flow chart of a control strategy according to an exemplaryembodiment of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 illustrates a power source 12 having an exemplary exhausttreatment system 10. The power source 12 may include an engine, such as,for example, a diesel engine, a gasoline engine, a natural gas engine,or any other engine apparent to one skilled in the art. The power source12 may, alternately, include another source of power, such as a furnaceor any other source of power known in the art.

The exhaust treatment system 10 may be configured to direct exhaustgases out of the power source 12, treat the gases, and introduce aportion of the treated gases into an inlet 21 of the power source 12.The exhaust treatment system 10 may include an energy extractionassembly 22 and a treatment element 19. The treatment element 19 mayinclude, for example, a regeneration device 20, a filter 16, and/or acatalyst 18. The exhaust treatment system 10 may further include arecirculation line 24 fluidly connected between the filter 16 and thecatalyst 18, and a flow cooler 26. The exhaust treatment system 10 maystill further include a flow sensor 28, a mixing valve 30, a compressionassembly 32, and an aftercooler 34.

A flow of exhaust produced by the power source 12 may be directed fromthe power source 12 to components of the exhaust treatment system 10 byflow lines 15. It is understood that the power source 12 may include oneor more combustion chambers (not shown) fluidly connected to an exhaustmanifold. In such an exemplary embodiment, the flow lines 15 may beconfigured to transmit a flow of exhaust from the combustion chambers tothe components of the exhaust treatment system 10 via the exhaustmanifold. The flow lines 15 may include pipes, tubing, and/or otherexhaust flow carrying means known in the art. The flow lines 15 may bemade of alloys of steel, aluminum, and/or other materials known in theart. The flow lines 15 may be rigid or flexible, and may be capable ofsafely carrying high temperature exhaust flows, such as flows havingtemperatures in excess of 700 degrees Celsius (approximately 1,292degrees Fahrenheit).

The energy extraction assembly 22 may be configured to extract energyfrom, and reduce the pressure of, the exhaust gases produced by thepower source 12. The energy extraction assembly 22 may be fluidlyconnected to the power source 12 by one or more flow lines 15 and mayreduce the pressure of the exhaust gases to any desired pressure. Theenergy extraction assembly 22 may include one or more turbines 14,diffusers, or other energy extraction devices known in the art. In anexemplary embodiment wherein the energy extraction assembly 22 includesmore than one turbine 14, the multiple turbines 14 may be disposed inparallel or in series relationship. It is also understood that in anembodiment of the present disclosure, the energy extraction assembly 22may, alternately, be omitted. In such an embodiment, the power source 12may include, for example, a naturally aspirated engine. As will bedescribed in greater detail below, a component of the energy extractionassembly 22 may be configured in certain embodiments to drive acomponent of the compression assembly 32.

In an exemplary embodiment, the regeneration device 20 of the treatmentelement 19 may be fluidly connected to the energy extraction assembly 22via flow line 15 and may be configured to increase the temperature of anentire flow of exhaust produced by the power source 12 to a desiredtemperature. The desired temperature may be, for example, a regenerationtemperature of the filter 16. Accordingly, the regeneration device 20may be configured to assist in actively regenerating the filter 16.Alternatively, the desired temperature may be, for example, a thresholdtemperature corresponding to the minimum passive regeneration orlight-off temperature of catalyst materials disposed downstream of theregeneration device 20. The desired temperature may also be a targettemperature corresponding to, for example, a peak conversion efficiencyrange of the catalyst materials. This peak conversion efficiency rangeof the materials may occur in the range of approximately 300 degreesCelsius to approximately 450 degrees Celsius, and in an exemplaryembodiment, the target temperature may be between approximately 300degrees Celsius and approximately 350 degrees Celsius. The targettemperature may also correspond to a minimum temperature setting of theregeneration device 20. As will be discussed below, such catalystmaterials may be disposed within a catalyst 18 of the exhaust treatmentsystem 10. Alternatively, such catalyst materials may be disposed withina filter 36 (FIG. 2) of the present disclosure. In another exemplaryembodiment, the regeneration device 20 may be configured to increase thetemperature of only a portion of the entire flow of exhaust produced bythe power source 12.

The regeneration device 20 may include, for example, a fuel injector andan ignitor (not shown), heat coils (not shown), and/or other heatsources known in the art. Such heat sources may be disposed within theregeneration device 20 and may be configured to assist in increasing thetemperature of the flow of exhaust through convection, combustion,and/or other methods. In an exemplary embodiment in which theregeneration device 20 includes a fuel injector and an ignitor, it isunderstood that the regeneration device 20 may receive a supply of acombustible substance and a supply of oxygen to facilitate combustionwithin the regeneration device 20. The combustible substance may be, forexample, gasoline, diesel fuel, reformate, and/or any other combustiblesubstance known in the art. The supply of oxygen may be provided inaddition to the relatively low pressure flow of exhaust gas directed tothe regeneration device 20 through flow line 15. In an exemplaryembodiment, the supply of oxygen may be carried by a flow of gasdirected to the regeneration device 20 from downstream of thecompression assembly 32 via a supply line 40. In such an embodiment, theflow of gas may include, for example, recirculated exhaust gas andambient air. It is understood that, in an exemplary embodiment of thepresent disclosure, the supply line 40 may be fluidly connected to anoutlet of the compression assembly 32. In an exemplary embodiment, theregeneration device 20 may be dimensioned and/or otherwise configured tobe housed within an engine compartment or other compartment of a workmachine (not shown) to which the power source 12 is attached. In such anembodiment, the regeneration device 20 may be desirably calibrated inconjunction with, for example, the filter 16, the energy extractionassembly 22, the catalyst 18, and/or the power source 12. Calibration ofthe regeneration device 20 may include, for example, among other things,adjusting the rate, angle, and/or atomization at which fuel is injectedinto the regeneration device 20, adjusting the flow rate of the oxygensupplied, adjusting the intensity and/or firing pattern of the ignitor,and adjusting the length, diameter, mounting angle, and/or otherconfigurations of a housing of the regeneration device 20. Suchcalibration may reduce the time required to regenerate the filter 16 andthe amount of fuel or other combustible substances needed forregeneration. Either of these results may improve the overall efficiencyof the exhaust treatment system 10. It is understood that the efficiencyof the exhaust treatment systems 10, 100 described herein may bemeasured by a variety of factors, including, among other things, theamount of fuel used for regeneration, the length of the regenerationperiod, and the amount (parts per million) of pollutants released to theatmosphere.

As shown in FIG. 1, the filter 16 of the treatment element 19 may beconnected downstream of the regeneration device 20. The filter 16 mayhave a housing 25 including an inlet 23 and an outlet 31. In anexemplary embodiment, the regeneration device 20 may be disposed outsideof the housing 25 and may be fluidly connected to the inlet 23 of thehousing 25. In another exemplary embodiment, the regeneration device 20may be disposed within the housing 25 of the filter 16. The filter 16may be any type of filter known in the art capable of extracting matterfrom a flow of gas. In an embodiment of the present disclosure, thefilter 16 may be, for example, a particulate matter filter positioned toextract particulate matter from an exhaust flow of the power source 12.The filter 16 may include, for example, a ceramic substrate, a metallicmesh, foam, or any other porous material known in the art. Thesematerials may form, for example, a honeycomb structure within thehousing 25 of the filter 16 to facilitate the removal of particulatematter. As discussed above, the particulate matter may include, forexample, soluble organic fraction, unburned hydrocarbons, and/or soot.

In an exemplary embodiment of the present disclosure, a portion of theexhaust produced by the combustion process may leak past piston sealrings within a crankcase (not shown) of the power source 12. Thisportion of the exhaust, often called “blow-by gases” or simply“blow-by,” may contain one or more of the exhaust gas componentsdiscussed above. In addition, because the crankcase is partially filledwith lubricating oil being agitated at high temperatures, the blow-bygases may also contain oil droplets and oil vapor. The blow-by gases maybuild up within the crankcase over time, thereby increasing the pressurewithin the crankcase. In such an embodiment, a ventilation line 42 maybe fluidly connected to the crankcase of the power source 12. Theventilation line 42 may also be fluidly connected to, for example, aport 46 disposed upstream of the filter 16 and/or the regenerationdevice 20.

The ventilation line 42 may comprise piping, tubing, and/or otherexhaust flow carrying means known in the art and may be structurallysimilar to the flow lines 15 described above. The ventilation line 42may include, for example, a check valve 44 and/or any other valveassembly known in the art. The check valve 44 may be configured toassist in controllably regulating a flow of fluid through theventilation line 42. In an exemplary embodiment, the check valve 44 maybe configured to assist in releasing built-up blow-by gases from thecrankcase.

The catalyst 18 of the exhaust treatment system 10 may be disposeddownstream of the filter 16. The catalyst 18 may contain catalystmaterials useful in collecting, absorbing, adsorbing, and/or storinghydrocarbons, oxides of sulfur, and/or oxides of nitrogen contained in aflow. Such catalyst materials may include, for example, aluminum,platinum, palladium, rhodium, barium, cerium, and/or alkali metals,alkaline-earth metals, rare-earth metals, or combinations thereof. Thecatalyst materials may be situated within the catalyst 18 so as tomaximize the surface area available for the collection of, for example,hydrocarbons. The catalyst 18 may include, for example, a ceramicsubstrate, a metallic mesh, foam, or any other porous material known inthe art, and the catalyst materials may be located on, for example, asubstrate of the catalyst 18.

As illustrated in FIG. 2, in an additional exemplary embodiment of thepresent disclosure, the filter 36 of the exhaust treatment system 100may include catalyst materials useful in collecting, absorbing,adsorbing, and/or storing hydrocarbons, oxides of sulfur, and/or oxidesof nitrogen contained in a flow. In such an embodiment, the catalyst 18(FIG. 1) may be omitted. The catalyst materials may include, forexample, any of the catalyst materials discussed above with respect tothe catalyst 18 (FIG. 1). The catalyst materials may be situated withinthe filter 36 so as to maximize the surface area available forabsorption, adsorption, and or storage. The catalyst materials may belocated on a substrate of the filter 36. The catalyst materials may beadded to the filter 36 by any conventional means, such as, for example,coating or spraying, and the substrate of the filter 36 may be partiallyor completely coated with the materials. It is understood that thepresence of catalyst materials, such as, for example, platinum and/orpalladium, upstream of the recirculation line 24 may result in theformation of sulfate in the exhaust treatment system 100. Accordingly,to minimize the amount of sulfate formed in the exemplary embodiment ofFIG. 2, only minimal amounts of catalyst materials may be incorporatedinto the filter 36.

It is also understood that the catalyst materials described above withrespect to FIGS. 1 and 2 may be capable of oxidizing one or morecomponents of an exhaust flow, such as, for example, particulate matter,hydrocarbons, and/or carbon monoxide. Thus, in the embodiment shown inFIG. 1, a portion of the particulate matter, hydrocarbons, and/or carbonmonoxide contained within the exhaust flow may be permitted to travelback to the power source 12 without being oxidized by the catalystmaterials. Although the catalyst materials discussed above may assist inthe formation of sulfate, the presence of these catalyst materials,either on a substrate of the filter 36 (FIG. 2) or in the catalyst 18(FIG. 1), may improve the overall emissions characteristics of theexhaust treatment systems 10, 100 by, for example, removing hydrocarbonsfrom the treated exhaust flow.

It is further understood that in the embodiment shown in FIG. 2, thecatalyst materials disposed on the substrate of the filter 36 may assistin passively regenerating the filter 36 during power source operation.As the power source 12 operates, particulates and other components ofthe power source exhaust may be trapped by the filter substrate. Theexhaust flow may reach temperatures in excess of, for example, 250degrees Celsius during normal operation of the power source 12 (i.e.,without operating the power source 12 in a manner so as to increase thetemperature of the exhaust by, for example, wastegating or otherconventional methods), and the exhaust gas may increase the temperatureof at least a portion of the filter substrate through convective heattransfer. At such temperatures, the components of the power sourceexhaust trapped by the substrate of the filter 36 may begin to reactwith the catalyst material located on the substrate. In particular, thecatalyst material may passively regenerate a portion of the filter 36 byoxidizing particulate matter trapped by the filter substrate as well ascarbon monoxide and/or hydrocarbons contained in the exhaust flow.Oxidation may occur at the passive regeneration or light-off temperatureof the filter 36 in which the catalyst material is hot enough to reactwith the components of the exhaust flow without additional heat beingprovided by, for example, the regeneration device 20. Such light-offtemperatures may be below the regeneration temperature of the filter 36.In an exemplary embodiment, a light-off temperature of the filter 36 maybe between approximately 250 degrees Celsius and approximately 350degrees Celsius.

Although at least a portion of the particulate matter contained withinthe filter 36 may be oxidized and/or removed therefrom through passiveregeneration, it is understood that, as shown in FIG. 2, an exemplaryexhaust treatment system 100 of the present disclosure may, nonetheless,include a regeneration device 20. Utilizing a catalyzed filter 36 inconjunction with a regeneration device 20 may assist in increasing theinterval between active regenerations. Increasing this interval mayreduce the amount of, for example, fuel burned during operation of thepower source 12 and may, thus, reduce the cost of operating the machineto which the power source 12 is connected. An exhaust treatment system100 including both a catalyzed filter 36 and a regeneration device 20may also enable filter manufacturers to include less catalyst material(such as, for example, precious metals) in the filter 36, therebyreducing the cost of the filter 36 and the overall cost of the system100.

Referring again to FIG. 1, the exhaust treatment system 10 may furtherinclude a recirculation line 24 fluidly connected downstream of thefilter 16. The recirculation line 24 may be disposed between the filter16 and the catalyst 18, and may be configured to assist in directing aportion of the exhaust flow from the filter 16 to the inlet 21 of thepower source 12. The recirculation line 24 may comprise piping, tubing,and/or other exhaust flow carrying means known in the art, and may bestructurally similar to the flow lines 15 described above. In anembodiment in which the exhaust treatment system 100 (FIG. 2) includes afilter 36 containing catalyst materials, the recirculation line 24 maybe disposed downstream of the filter 36 and upstream of an exhaustsystem outlet 17.

The flow cooler 26 may be fluidly connected to the filter 16 via therecirculation line 24 and may be configured to cool the portion of theexhaust flow passing through the recirculation line 24. The flow cooler26 may include a liquid-to-air heat exchanger, an air-to-air heatexchanger, or any other type of heat exchanger known in the art forcooling an exhaust flow. In an alternative exemplary embodiment of thepresent disclosure, the flow cooler 26 may be omitted.

The mixing valve 30 may be fluidly connected to the flow cooler 26 viathe recirculation line 24 and may be configured to assist in regulatingthe flow of exhaust through the recirculation line 24. It is understoodthat in an exemplary embodiment, a check valve (not shown) may befluidly connected upstream of the flow cooler 26 to further assist inregulating the flow of exhaust through the recirculation line 24. Themixing valve 30 may be a spool valve, a shutter valve, a butterflyvalve, a check valve, a diaphragm valve, a gate valve, a shuttle valve,a ball valve, a globe valve, or any other valve known in the art. Themixing valve 30 may be actuated manually, electrically, hydraulically,pneumatically, or in any other manner known in the art. The mixing valve30 may be in communication with a controller (not shown) and may beselectively actuated in response to one or more predeterminedconditions.

The mixing valve 30 may also be fluidly connected to an ambient airintake 29 of the exhaust treatment system 10. Thus, the mixing valve 30may be configured to control the amount of exhaust flow entering a flowline 27 relative to the amount of ambient air flow entering the flowline 27. For example, as the amount of exhaust flow passing through themixing valve 30 is desirably increased, the amount of ambient air flowpassing through the mixing valve 30 may be proportionally decreased andvice versa.

As shown in FIG. 1, the flow sensor 28 may be fluidly connected to therecirculation line 24 downstream of the flow cooler 26. The flow sensor28 may be any type of mass air flow sensor, such as, for example, a hotwire anemometer or a venturi-type sensor. The flow sensor 28 may beconfigured to sense the amount of exhaust flow passing through therecirculation line 24. It is understood that the flow cooler 26 mayassist in reducing fluctuations in the temperature of the portion of theexhaust flow passing through the recirculation line 24. Reducingtemperature fluctuations may also assist in reducing fluctuations in thevolume occupied by a flow of exhaust gas since a high temperature massof gas occupies a greater volume than the same mass of gas at a lowtemperature. Thus, sensing the amount of exhaust flow through therecirculation line 24 at positions downstream of the flow cooler 26(i.e., at a relatively controlled temperature) may result in moreaccurate flow measurements than measurements taken upstream of the flowcooler 26. It is further understood that the flow sensor 28 may alsoinclude, for example, a thermocouple (not shown) or other deviceconfigured to sense the temperature of the exhaust flow.

The flow line 27 downstream of the mixing valve 30 may direct theambient air/exhaust flow mixture to the compression assembly 32. Thecompression assembly 32 may include a compressor 13 configured toincrease the pressure of a flow of gas at a desired pressure. Thecompressor 13 may include a fixed geometry-type compressor, a variablegeometry-type compressor, or any other type of compressor known in theart. In the exemplary embodiment shown in FIG. 1, the compressionassembly 32 may include more than one compressor 13, and the multiplecompressors 13 may be disposed in parallel or in series relationship. Acompressor 13 of the compression assembly 32 may be connected to aturbine 14 of the energy extraction assembly 22, and the turbine 14 maybe configured to drive the compressor 13. In particular, as hot exhaustgases exit the power source 12 and expand against the blades (not shown)of the turbine 14, components of the turbine 14 may rotate and drive theconnected compressor 13. Alternatively, in an embodiment in which theturbine 14 is omitted, the compressor 13 may be driven by, for example,the power source 12, or by any other drive known in the art. It is alsounderstood that in a nonpressurized air induction system, thecompression assembly 32 may be omitted.

The aftercooler 34 may be fluidly connected to the power source 12 viathe flow line 27 and may be configured to cool a flow of gas passingthrough the flow line 27. In an exemplary embodiment, this flow of gasmay be the ambient air/exhaust flow mixture discussed above. Theaftercooler 34 may include a liquid-to-air heat exchanger, an air-to-airheat exchanger, or any other type of flow cooler or heat exchanger knownin the art. In an exemplary embodiment of the present disclosure, theaftercooler 34 may be omitted, if desired.

The exhaust treatment system 10 may further include a condensate drain38 fluidly connected to the aftercooler 34. The condensate drain 38 maybe configured to collect a fluid, such as, for example, water or othercondensate formed at the aftercooler 34. It is understood that suchfluids may consist of, for example, condensed water vapor contained inrecycled exhaust gas and/or ambient air. In such an exemplaryembodiment, the condensate drain 38 may include a removably attachablefluid tank (not shown) capable of safely storing the condensed fluid.The fluid tank may be configured to be removed, safely emptied, andreconnected to the condensate drain 38. In another exemplary embodiment,the condensate drain 38 may be configured to direct the condensed fluidto a fluid container (not shown) and/or other component or location onthe work machine. Alternatively, the condensate drain 38 may beconfigured to direct the fluid to the atmosphere or to the surface bywhich the work machine is supported.

INDUSTRIAL APPLICABILITY

The exhaust treatment systems 10, 100 of the present disclosure may beused with any combustion-type device, such as, for example, an engine, afurnace, or any other device known in the art where the recirculation ofreduced-particulate exhaust into an inlet of the device is desired. Theexhaust treatment systems 10, 100 may be useful in reducing the amountof harmful exhaust emissions discharged to the environment. The exhausttreatment systems 10, 100 may also be capable of purging the portions ofthe exhaust gas captured by components of the system through aregeneration process.

As discussed above, the combustion process may produce a complex mixtureof air pollutants. These pollutants may exist in solid, liquid, and/orgaseous form. In general, the solid and liquid pollutants may fall intothe three categories of soot, soluble organic fraction, and unburnedhydrocarbons. The soot produced during combustion may includecarbonaceous materials, and the soluble organic fraction may includeunburned hydrocarbons that are deposited on or otherwise chemicallycombined with the soot.

Due to increasing concerns about the health of the environment, theEnvironmental Protection Agency has mandated that, for 2007, hydrocarbonemissions for on-highway vehicles must be less than or equal to 0.14grams/horsepower hour. Various exhaust treatment strategies are requiredin order to meet these stringent emissions requirements at substantiallyall power source operating conditions. For example, as will be discussedbelow, components of the exhaust treatment systems 10, 100 such as, forexample, the catalyst materials, may be heated when the vehicle isoperated at low exhaust temperature conditions. Such conditions mayexist, for example, upon start-up of the power source 12 and during aprolonged period of time in which the power source 12 operates at ornear idle. In such conditions, the catalyst materials may be below theirlight-off temperature, and heating the catalyst materials may assist inincreasing their conversion efficiency. The operation of the exhausttreatment systems 10, 100 will now be explained in detail. Unlessotherwise noted, the exhaust treatment system 100 of FIG. 2 and thecontrol strategy 50 illustrated in FIG. 3 will be referred to for theduration of the disclosure.

At start-up (step 52), sensors of the exhaust treatment system 100 maysense parameters of the power source 12 and/or the exhaust treatmentsystem 100. Such parameters may include, for example, engine speed,engine temperature, exhaust flow temperature, exhaust flow pressure,and/or particulate matter content. The sensors may also be electricallyconnected to a controller (not shown) and may be configured to sendsignals containing sensed information to the controller. For example, atemperature sensor 48 may be disposed proximate the outlet 31 of thefilter 36 and may be configured to sense the temperature of the exhaustflow exiting the filter 36. Alternatively, the temperature sensor 48 maybe disposed proximate an outlet of the catalyst 18 (FIG. 1).Accordingly, the temperature sensor 48 may be configured to sense atemperature representative of catalyst material temperature (step 54)and may also be configured to send signals indicative of the sensedtemperature to the controller on a substantially continuous basis. Thesensed temperature may be representative of the temperature of thecatalyst materials at start-up of the power source 12 and/or during aprolonged low exhaust temperature operation of the power source 12.

Upon receiving, for example, temperature information sent by thetemperature sensor 48, the controller may store the information forfurther use. The controller may also manipulate the information in anyconventional mathematical and/or statistical way, such as, for example,by entering the information into one or more preset algorithms used tocontrol one or more components of the exhaust treatment system 100. Forexample, the controller may compare the sensed temperature to apredetermined threshold temperature (step 56). The threshold temperaturemay correspond, for example, to the light-off temperature of thecatalyst materials disposed within the filter 36, and in an exemplaryembodiment, the threshold temperature may be approximately 250 degreesCelsius. If the sensed temperature is above the predetermined thresholdtemperature, the exhaust treatment system 100 may continue to operateaccording to a steady state control strategy (step 58) stored within thecontroller. The steady state control strategy may apply to situationswhere, for example, the temperature of the catalyst materials within thefilter 36 is above the light-off temperature of the catalyst materials.If, on the other hand, the sensed temperature is below the predeterminedthreshold temperature, the controller may ignite the regeneration device20 (step 60).

Igniting the regeneration device 20 may include a number of systemverification processes, such as, for example, sensing the pressureand/or flow rate of the combustible substance and supply of oxygen beingdirected to the regeneration device 20 for combustion, and substantiallyblocking a flow of recirculated exhaust gas from entering the mixingvalve 30 (and, thus, from entering the inlet 21 of the power source 12).Igniting the regeneration device 20 may also include, for example,energizing the ignitor, injecting the combustible substance, andregulating the supply of oxygen passing to the regeneration device 20.

Once the regeneration device 20 has been ignited, the regenerationdevice 20 may be controlled to operate at a target temperature (step62). The target temperature may correspond to the minimum temperaturesetting of the regeneration device 20 and may be within a peakconversion efficiency range of the catalyst materials. For example, inan embodiment of the present disclosure, the target temperature may bebetween approximately 300 degrees Celsius and approximately 350 degreesCelsius. Operating the regeneration device 20 in this way may heat theexhaust gas flowing therethrough to the target temperature and may beginto increase the temperature of the catalyst materials of the filter 36through convection and/or conduction. Accordingly, a temperature of theexhaust flow measured by a temperature sensor 49 disposed upstream ofthe catalyst materials should be equal to the target temperature.

The controller may also modify one or more control parameters of theexhaust treatment system 100 (step 64), and such modifications mayapproximate the control parameters utilized during regeneration of thefilter 36. For example, the controller may modify the position and/orother settings of the mixing valve 30. Such modified settings may allowa flow of recirculated exhaust gas to once again enter the mixing valve30, but may result in a relative decrease in the amount of recirculatedexhaust gas being supplied to the inlet 21 of the power source 12compared to the steady state control strategy discussed above. In anexemplary embodiment, the amount of recirculated exhaust gas beingsupplied to the inlet 21 may be reduced by as much as approximately 50percent under these modified settings. The controller may also modifythe timing of one or more intake valves (not shown) associated with theinlet 21 and may alter the boost level of the energy extraction assembly22.

The temperature sensors 48, 49 may then be used to sense a temperatureupstream and downstream of the catalyst materials (step 66). Asdiscussed above, the temperature of the exhaust flow upstream of thecatalyst materials may be raised to the target temperature by way of theregeneration device 20. Thus, the temperature sensed by temperaturesensor 49 may be approximately equal to the target temperature. Thetemperature sensed by temperature sensor 48, on the other hand, mayapproximate the temperature of the catalyst materials and/or the filter36, and may initially be less than a temperature sensed upstreamthereof. The temperature sensors 48, 49 may send signals containing thissensed temperature information to the controller, and the controller maydetermine whether the temperature sensed downstream of the catalystmaterials is greater than or equal to the target temperature (step 68).

If the temperature sensed downstream of the catalyst materials is lessthan the target temperature, the regeneration device 20 may becontrolled to continue heating the exhaust gas to the targettemperature, and the temperature sensors 48, 49 may continue to sensetemperatures upstream and downstream of the catalyst materials (step66). If, on the other hand, the temperature sensed downstream of thecatalyst materials is greater than or equal to the target temperature,the controller may command the regeneration device 20 to continueburning at the target temperature for a predetermined period of time(step 70). The predetermined period of time may be any desirable lengthof time useful in ensuring that the entire substrate, mesh, and/or otherstructure on which the catalyst materials are disposed has substantiallyuniformly reached the target temperature. Holding the regenerationdevice 20 at the target temperature for the predetermined period of timemay also substantially mitigate any errors in the sensed temperaturevalues. In an exemplary embodiment of the present disclosure, thepredetermined period of time may be 90 seconds. Once the predeterminedperiod of time has expired, the regeneration device 20 may be turned off(step 72) and the control parameters of the exhaust treatment system 100that were modified in step 62 may be reset to the values, positions,and/or settings that were operative at start-up (step 74). The values,positions, and/or settings of the control parameters selected in step 74may be substantially the same as those utilized by the steady statecontrol strategy of step 58.

Controlling the components of the exhaust treatment system 100 in thisway may assist in reducing, for example, the particulate matteremissions of the power source 12. In particular, rapidly increasing thetemperature of the catalyst materials disposed within the exhausttreatment system 100 to at least their light-off temperature may assistin reducing hydrocarbon emissions of the power source 12 at start-up. Asdiscussed above, once the catalyst materials reach their light-offtemperature, the catalyst materials may oxidize substantially all of thehydrocarbon present in an exhaust flow of the power source 12, therebyreducing the amount of harmful pollutants released to the environmentand minimizing the levels of whitesmoke and undesirable odors emitted bythe exhaust treatment system 100.

Other embodiments of the disclosed exhaust treatment systems 10, 100will be apparent to those skilled in the art from consideration of thespecification. For example, the systems 10, 100 may include additionalfilters, such as, for example, a sulfur trap disposed upstream of thefilter 36. The sulfur trap may be useful in capturing sulfur moleculescarried by the exhaust flow. It is intended that the specification andexamples be considered as exemplary only, with the true scope of theinvention being indicated by the following claims.

1. A method of controlling an exhaust treatment system, comprising:sensing a temperature representative of a catalyst material temperatureat start-up of a power source; comparing the sensed temperature to athreshold temperature; igniting a regeneration device of the exhausttreatment system in response to the comparing, the regeneration devicebeing disposed upstream of the catalyst material; and operating theregeneration device at a target temperature.
 2. The method of claim 1,further including modifying a control parameter of the exhaust treatmentsystem in response to the comparing.
 3. The method of claim 2, whereinmodifying the control parameter includes modifying at least one of aposition of a mixing valve, a timing of an intake valve associated withthe power source, and a boost level of an energy extraction assembly. 4.The method of claim 1, further including sensing a first temperature ata location upstream of the catalyst material and a second temperature ata location downstream of the catalyst material.
 5. The method of claim4, further including comparing the first temperature to the secondtemperature and operating the regeneration device at the targettemperature for a predetermined period of time in response to thecomparison between the first and second temperature.
 6. The method ofclaim 1, further including turning off the regeneration device andmodifying a control parameter of the exhaust treatment system.
 7. Themethod of claim 1, wherein the threshold temperature is a light-offtemperature of the catalyst material.
 8. The method of claim 1, whereinthe target temperature is between approximately 300 degrees Celsius andapproximately 350 degrees Celsius.
 9. An emissions control method for aninternal combustion engine, comprising: igniting a regeneration devicefluidly connected to the internal combustion engine; increasing atemperature of a catalyst material to a target temperature during a lowexhaust temperature operation of the internal combustion engine; andmaintaining the temperature of the catalyst material at the targettemperature for a predetermined period of time.
 10. The method of claim9, further including sensing a temperature representative of a catalystmaterial temperature at start-up.
 11. The method of claim 10, furtherincluding modifying a control parameter of an exhaust treatment systemassociated with the internal combustion engine in response to thesensing.
 12. The method of claim 9, wherein increasing the temperatureof the catalyst material assists in oxidizing particulate mattercontained within an exhaust flow of the internal combustion engine. 13.The method of claim 12, wherein the particulate matter includes at leastone of soot, soluble organic fraction, and unburned hydrocarbons. 14.The method of claim 9, wherein the target temperature is betweenapproximately 300 degrees Celsius and approximately 350 degrees Celsius.15. The method of claim 9, further including passively regenerating aparticulate filter fluidly connected to the internal combustion enginedownstream of the regeneration device.
 16. The method of claim 9,wherein the catalyst material is disposed on a substrate of aparticulate filter.
 17. An exhaust treatment system of a power source,comprising: a catalyst material; a regeneration device disposed upstreamof the catalyst material and configured to increase a temperature of thecatalyst material to a target temperature at start-up of the powersource and in response to a sensed parameter of the exhaust treatmentsystem; and a particulate filter configured to extract components froman exhaust flow of the power source.
 18. The system of claim 18, whereinthe sensed parameter of the exhaust treatment system is a temperaturerepresentative of the catalyst material at start-up of the power source.19. The system of claim 18, wherein the target temperature is betweenapproximately 300 degrees Celsius and approximately 350 degrees Celsius.20. The system of claim 18, further including a first temperature sensordisposed upstream of the catalyst material and a second temperaturesensor disposed downstream of the catalyst material.